The driving behavior of motor vehicles, in particular of commercially used vehicles for the transport of loads, can be influenced considerably by the load state. Therefore, various methods for estimating the mass of the vehicle have already become known that only use the signals of the sensors provided for drive dynamics control. If the longitudinal dynamics of the vehicle during an acceleration process are considered, then a balance of forces can be analyzed and the mass of the vehicle can be calculated as the quotient of the difference between the driving and decelerating forces in the denominator and the resulting acceleration in the numerator.
In order to take into account the influence of a gradient during the estimation of the mass of the vehicle, it is known from DE 10 2006 012 246 A1 to measure the longitudinal acceleration with an acceleration sensor. An offset or an additive displacement of the longitudinal acceleration signal can however result in a significant deviation between the actual and estimated masses of the vehicle. Furthermore, an offset of the longitudinal acceleration sensor adversely affects the operation of a hill start aid, because the hill start aid generally adjusts the holding pressure according to the measured gradient or downhill force.
An additive displacement or an offset of the longitudinal acceleration signal can occur for example owing to an inclined installation of the sensor, a temperature change or asymmetrical loading of the vehicle. Whereas an obliquely installed sensor causes a constant or permanent offset, temperature changes or a changed load result in fluctuating or time-varying offsets. In this case the temperature influence can for example be corrected using a characteristic curve if there is a temperature sensor present.
In WO 2005/101031 A1, a method for offset compensation of the electrical signal of a sensor (in particular of an acceleration sensor) is described, with which a compensation value is updated over the long term during the service life of the sensor, wherein the updating is carried out depending on the distance traveled by the vehicle. Based on the assumption that the generation of an average value over a sufficiently large number of measurement values or a sufficiently long stretch of a gradient gives a value of zero, a permanent or slowly varying offset (for example owing to ageing of the sensor) can thus be corrected. The influence of loading changing from journey to journey cannot be taken into account with said method.
From DE 10 2005 025 851 B1, a method for detecting a change of the weight distribution in a vehicle is known, with which after switching off the ignition a first value for the tilt of the vehicle is determined, after switching on the ignition a second value for the tilt of the vehicle is determined, and using a comparison of the first and second values for the tilt of the vehicle a change of the weight distribution in the vehicle can be detected. By means of said method, thus only the offset is determined that is caused by the loading that is carried out during the last period in which the vehicle is at a standstill. It is not ensured thereby that a currently present offset will be adequately compensated.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.